System and method for cutting pattern pieces from sheet material

ABSTRACT

A system and method for cutting multiple pattern pieces from a layup of sheet material employing two-stage digitizing to produce a cutting program in which contour segments of individual pieces are cut by a cutting blade in different directions about the pattern pieces. The direction in which a particular segment of a pattern piece contour is cut and the order in which the segments are cut are selected to most easily facilitate the cutting operation. The point on any given pattern piece toward which a cutting blade is advanced from different directions is generally the point of closest approach to an adjacent or contiguous pattern piece in the marker cut in the sheet material. The feed rate and tangency of the cutting blade are also regulated at sensitive cutting points such as the points of closest approach to an adjacent pattern piece.

nited States Patent Pearl et a1.

[ Apr. 16, 1974 Gerber Garment Technology, Inc., East Hartford, Conn.

Filed: Dec. 11,1972

Appl. N0.: 314,144

[73] Assignee:

52 US. Cl 83/56, 83/71, 83/747, 83/925 cc 1m. Cl. B26d 1/10, A4lh 43/00Field of Search 83/13, 56, 71, 747, 925 CC [56] References Cited UNITEDSTATES PATENTS 3,477,322 11/1969 Gerber....; 83/71 Primary Examiner-J.M. Meister Attorney, Agent, or FirmMcCormick, Paulding & Huber [5 7]ABSTRACT A system and method for cutting multiple pattern pieces from alayup of sheet material employing twostage digitizing to produce acutting program in which contour segments of individual pieces are cutby a cutting blade in' different directions about the pattern pieces.The direction in which a particular segment of a pattern piece contouris cut and the order in which the segments are out are selected to mosteasily facilitate the cutting operation. The point on any given patternpiece toward which a cutting blade is advanced from different directionsis generally the point of closest approach to an adjacent or contiguouspattern piece in the marker cut in the sheet material. The feed rate andtangency of the cutting blade are also regulated' at sensitive cuttingpoints such as the points of closest approach to an adjacent patternpiece.

10 Claims, 8 Drawing Figures MARKER X46 PATTERN k DATA A B D1G|TIZERMEMORY PROCESSOR ,44 RECORDER MARKER GENERATOR 1 POINT BASIC DATACOMMANDS 42 26 DIGITIZER l TAPE I 40 --"'1 ll 1 I :2 28 1 E q; l F ICUT'TlNG CONTROLLER I 1 TABLE I l i l PMENTEHAPR 16 m4 SHEH 10? A O R 5O s f w AC 0 R P r 3 4 PATTERN LMEMORY RECORDER R E E W m D Q 4 D E E Km M AC MARKER GENERATOR BASIC POI NT COMMANDS D ATA DIGITIZER TAPECONTROLLER A.

PATENTEBAPR 161974 3,803,960

sum 2 M A v PATENIEIIIIPR 16 I974 803; 96 O SHEET 3 IIF A DATA PROCESSORLOCATE PATTERN PIECES IN PATTERN MEMORY 8|\ LOCATE CONTOUR SEGMENTSIDENTIFIED ON MARKER V 82 READ DATA POINTS BETWEEN IDENTIFIED SEGMENTSCLOCKWISE READ DATA POINTS ALONG 83\ IDENTIFIED SEGMENTS COUNTER CL0CIwISE 84\ DELETE DATA POINTS WITHIN SELECTED SEGMENTS 88 II ADD DATAPOINTS OF SELECTED SEGMENTS NOT ADD CuT PREVIOUSLY SLOWDOWN PROCESS DATAPOINTS BGI BY STANDARD SERvO AND CURVE ALGORITHMS w STORE CUTTINGPROGRAM ADD YAW COMPENSATION SYSTEM AND METHOD FOR CUTTING PATTERNPIECES FROM SHEET MATERIAL BACKGROUND OF THE INVENTION The presentinvention relates to an automatically controlled cutting machine inwhich a cutting blade is advanced along a cutting path in accordancewith programmed commands. More particularly, the present inventionrelates to a system in which pattern pieces are cut from sheet materialby programming the cutting blade to advance along different contouredsegments of a pattern piece in different directions about the patternpiece.

Numerically controlled cutting machines of the type disclosed in U.S.Pat. No. 3,347,121 to Wiatt and No. 3,495,492 to Gerber et al., are wellknown in the art and are used for cutting large numbers of patternpieces from layups of sheet material. One primary advantage offered bythe automaticallycontrolled cutting machines is their ability to cutclosely nested pattern pieces from the layups and to reduce waste andthe cost of materials.

The closer nesting of patterns within a layup, however, is not withoutcertain difficulties which arise due to the inherent characteristics ofa cutting operation in which a rotating or reciprocating blade orequivalent mechanical cutting tool is moved in cutting contact with thesheet material. In particular, difficulties arise where one cutting pathextends'in close proximity to another. When the first cut is made alongone of two adjacent cutting paths, there is no difficulty because it isnot material to the cutting operation that an adjacent cut iscontemplated. However, when the second cut is made adjacent the previouscut, the rigidity of the sheet material, which is necessary for anaccurate cut, decreases, generally with the distance between the cuttingpaths. Furthermore, where segments of adjacent cut ting paths extendgenerally tangent to one another, that is, in either contacting orclosely spaced relationship to each other, limp sheet material such aswoven and nonwoven fabrics used to manufacture apparel will shift ormove away from a cutting blade and distort a properly programmed contourinthe finished piece. Apparatus such as disclosed in U.S. Pat. No.3,495,492, referenced above rigidizes limp sheet material to a degree.Nevertheless, it has been found that the difficulties of cutting alongclosely spaced or generally tangent cutting paths can be further reducedby controlling cutting parameters relating to the movement of thecutting blade through the material at the sensitive points, the pointsof tangency or close approach.

It is accordingly a general object of the present invention to disclosea system and method for cutting pattern pieces from limp sheet materialat sensitive points by controlling selected cutting parameters in anautomatically controlled cutting machine.

SUMMARY OF THE INVENTION The present invention resides in a system andmethod for cutting pattern pieces from sheet material by means ofaprogram controlled cutting machine. The principal features of theinvention relate to the generation of a cutting program and the stepscarried out by the cutting machine in response to the cutting program.

The invention in one form is related to a system from which the cuttingprogram is generated by initially reducing the contours of the patternpieces in a marker layup to point data form by a two-stage digitizingprocess. Each segment of the pattern contours is identified by pointdata and the cutting direction along the seg' ment. The direction ofcutting along a given contour, and the order to cutting the contours isdefined by the order in which the point data is arranged or called forin the program. Such order is obtained by digitizing the contoursegments in one direction and by rearranging the data after digitizingin a standardized order.

With the data arranged in the order necessary for the proper cuttingdirection about a given pattern piece, it is then processed in thesystem by conventional data processing techniques used in the past togenerate cutting commands intelligible to the cutting machine. Theprocessed data may then be recorded in a memory device, such as apunched or magnetic tape, or may be utilized directly by the cuttingmachine to execute a cutting operation.

The program generated by the above system permits a cutting tool to beadvanced along a cutting path defined by the contours of a patternpiecein both the clockwise and counterclockwise directions. The program alsopermits certain contour segments to be cut before others. It isadvantageous to cut in this manner since it allows the tool to approachsensitive points, such as a point of tangency or a point closest to thecontour of an adjacent piece, from two directions and to alleviatedifficulties by making certain cuts before others. The ability to cut intwo directions or establish cut priorities is referred to as cuttingprotocol. Cutting protocol eases the task of cutting closely nestedpattern pieces in a marker layout.

A further factor in cutting protocol is the manner in which a cut isexecuted. Two special techniques comprise introducing into the-cuttingprogram reduced feedrate commands and directional bias commands at Isensitive points. The bias commands cause a cutting blade to be rotatedout of a tangent position at any point along the cutting path and awayfrom an adjacent and previously made cut.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of acutting machine which can be utilized to cut a plurality of patternpieces from layups of sheet material in accordance with the presentinvention.

. FIG. 2 is a block diagram of a complete cutting system'includingcomponents for generating a cutting program and the machine in FIG. 1.

FIG. 3 is an enlarged plan view of one portion of a marker showing amethod of cutting in accordance with the present invention.

FIG. 4 is an enlarged plan view of another portion of a marker cut inaccordance with the present invention.

FIG. 5 is an enlarged plan view of still another por-' tion a marker cutin accordance with the present invention.

FIG. 6 is a flow chart depicting the operations of the data processor inFIG. 2.

FIG. 7 is a flow diagram of the feedrate subroutine utilized by the dataprocessor in FIG. 2.

FIG. 8 is a flow diagram of the blade angle subroutine utilized by thedata processor in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 discloses anautomatically controlled cutting machine having a cutting table 12 whichis utilized in the present invention for cutting a plurality of patternpieces from sheet material spread on the table. The cutting machine hasa multitudeof uses but is now frequently found in the apparel andupholstering industries where a plurality of pattern pieces are cut fromlimp sheet material such as a woven or non-woven fabric. After a cuttingoperation, the cut pieces are removed from the table 12 and assembled infinished form as articles of clothing or upholstery.

In cutting machines of the type illustrated, the sheet material isspread in a multi-tier layup L on the support surface 14 of the table12. The layup is held in position by, for example, an air imperviousoverlay 16 and a vacuum system incorporated in the bed of the table asdescribed in greater detail in U.S. Pat. No. 3,495,492 referenced above.I

A cutting tool such as a reciprocating knife blade 20 is translated overthe layup in the illustrated X and Y coordinate directions by means ofan X carriage 22 and a Y carriage 24, respectively, forming mechanizedportions of the table 12. The tool 20 is also rotated in a controlledmanner about a 0 axis perpendicular to the X and Y axes and the supportsurface 14 so that the knife is oriented generally tangent to a cuttingpath at each point.

The movements of the cutting blade 20 through the layup L are programmedin a memory device such as the punched tape 26. Basic cutting commandson the tape are read by a controller 28 and converted by the controllerinto signals intelligible to the motor controls of the cutting table 12.The commands are transmitted to the cutting table through the cable 30and regulate the blade motions relative to the X-, Y- and O-axes as wellas the drive motors which lift and reciprocate the blade 20. Additionalauxiliary commands may also be transmitted to the cutting table tocontrol drilling, marking and other functions related to the cuttingoperation.

FIG. 2 shows the complete cutting system including the components whichgenerate the program tapes 26 for cutting a a plurality of patternpieces from sheet material on the table 12. It will be readilyunderstood that once program tapes have been generated for markers, thegrouped pattern pieces to be cut in the sheet material, it is onlynecessary to change the tape read by the controller 28 to change themarker patterns and the cutting operation. The controller 28 and cuttingtable 12 do not differ from the controllers and table known in the priorart. The entire system, however, which generates the program tapesdefining the cutting operations, the method by which the tapes aregenerated in this system and the cutting methods disclosed areconsidered to be new and are described in greater detail below.

The primary information needed to generate a program tape is theconfiguration of the pattern pieces to be cut. Exemplary patternpieces'are illustrated in the plaque 40 of FIG. 2, each pattern piecebeing identified by a letter. The pattern pieces may represent portionsof clothing or upholstering which are to be manufactured from fabricmaterial cut on the table 12. The contours of the pattern pieces areinitially reduced to point data by means of a coordinate digitizer 42.The digitizer 42 is conventional and is operated manually orautomatically as described in U.S. Pat. No. 3,609,237 issued Sept. 28,l97l to trace the contour of each pattern piece and produce signalsrepresenting the coordinates of spaced points along the contours. In thedigitizing process, a reticle or other optical index is moved along thecontour of each pattern piece in a given direction and, as thedigitizing process progresses, the data points for the individualpattern pieces are recorded sequentially in a buffer or pattern memory43 at specified addresses. The data points at any given address are,therefore, listed in the same order in which the points have beendigitized. Sufficient data points are recorded to fully define theimportant contours of a pattern piece so that a cutting tool, commandedto move between the recorded points in the same order in which thepoints appear in the memory, tracks the contours of a given patternpiece in the same direction as digitized.

After the pattern pieces have been individually digitized, the pointdata is fed to a marker generator 44 which produces a marker layout 46.The marker layout defines the relative positioning of the pattern pieceswith respect to one another and with respect to the perimeter of sheetmaterial-from which the pattern pieces are to be cut. Therefore, themarker layout, sometimes referred to simply as the marker, representsthe relative placement of the pattern pieces in a closely nestedarrangement to be cut from the sheet material. The marker generator 44may be the type disclosed in U.S. Pat. No. 3,596,068 which optimizesmaterial utilization. Computerized marker generators which automaticallyoptimize material utilization include a packing subroutine whicheffectively shifts the pattern pieces within the boundaries of a markeruntil the amount of material required for the pieces to be cut is aminimum. The pattern pieces in the marker layout after the packingoperation are closely nested and frequently have points of tangency orcommon contour segments between adjacent pieces. Although close nestingis desirable from the standpoint of material economics, the cuttingoperation can be made very difficult by that condition.

The generation of the marker layout 46 can also be performed manuallywithout the generator 44. In this case, the output of digitizer 42 ismerely stored for future use.

A third, semi-automatic method of generating the marker employs aninteractive graphics process. In this process the pattern pieces aredisplayed on a tablet or cathode ray tube (CRT) connected to a datacomputer in which the contours of the individual pieces are stored. Anindex instrument such as an electrical wand or light pen interactingwith the tablet or CRT is manipulated over the display to shift thepattern pieces into various positions and obtain close nesting by atrialand-error process resembling the entirely manual process of makingmarkers. When the final grouping is arrived at, the display is frozen.

Once a marker layout 46 is generated, the positioning of the individualpattern pieces within the boundaries of the marker and relative to oneanother is stored in the memory 43 by transmitting point data definingthe marker directly to the memory from the generator 44 or by reducingthe marker display to point data by the digitizer 48. Separatedigitizers 42 and 48 are represented in FIG. 2 and the constructionofthe digitizers may be the same or different depending upon thedigitizing processes selected. If the processes are both manual andperformed at different times, the same digitizer may be used at eachstage of the programming process.

The process in which, first, the pattern pieces are individuallydigitized and, second, the placement of the patternpieces on the markerlayout is digitized is referred to as a two-stage digitizing process. Inthe first stage, in addition to digitizing the full contour of eachpattern piece, it is necessary to establish geometric reference pointsfor each pattern piece such as those points indicated by crosses in theplaque 40. During the second stage of digitizing either the referencepoints of the individual pattern pieces are located relative to theperiphery of the layout and stored in the memory 43, or data within thegenerator 44 identifying the positional relationship of the pieces inthe layout is transmitted to the memory. It will be noted that with twostage digitizing, a given pattern piece is completely digitized onlyonce even though the piece appears in the marker more than once.

With the position of each pattern piece located relative to the markerlayout and each individual pattern piece digitized, the marker layout iscompletely defined in the memory 43 so that in subsequent operations ofthe data processor 50, all data points defining the pattern piececontours can be referenced to the marker layout.

The point data received from the memory 43 by the data processor 50 iseffectively raw data defining only the contours to be cut from a layupof sheet material on the cutting table 12. Raw data cannot be feddirectly to the cutting machine but must be converted into a form ofbasic machine commands intelligible to the cutting machine. For example,the basic commands must be correlated with the feedrate capacity of thecutting machine which is limitedby the servo motors driving the carriageand the cutting blade. Other'limitations of the cutting machine requirethat the cutting blade be lifted, rotated and then plunged throughthelayup to cut sharp corners during a cutting operation. Furthermore,in accordance with the present invention, the cutting blade is moved ina particular manner about a pattern piece in order to cut the desiredcontours most accurately with the least difficulty.

To this end the raw point data is operated upon by the data processor 50to produce basic machine commands atthe processor output. If the basiccommands are not to be utilized immediately, recorder 52 makes apermanent record of the commands on the program tape 26. The tape 26 ismerely a memory device which preserves the basic commands until they areread by the controller 28 during a cutting operation.

Turning, then, more particularly to the present invention, reference ismade to FIG. 3 which is-an enlarged portion of the marker layout intheregion including adjacent pattern pieces. A and B. Due to the closelynested relationshipof the pattern pieces, pieces A and B are tangent ata point 60 of closest approach. A point of tangency of the typeillustrated poses a cutting problem with limp sheet material because thematerials are incapable of rigidly supporting themselves in'the regionof the tangent contours after the first cut through point 60. Theproblem is present wherever adjacent contours are generally tangent,that is either precisely tangent at a single point of contact or merelyin closely spaced but noncontacting relationship with one another.

For example, it will be assumed that piece A is cut before piece B. Asthe blade traverses the tangent contour of piece A at point 60, theblade is always moving into virgin material, that is, material which hasnot been cut and therefore is fully supported by adjacent material. Ifthe cutting blade is subsequently called upon to pass through pointwhile following the curved contour of piece B, counterclockwise frompoint 58, the knife may be caused to deviate from a true cutting pathtoward the piece A as it approaches point 60 because the sliver ofmaterial between the blade and the previous cut along the contour ofpiece A is less firmly supported than the material within the contour ofpiece B and the forces in the material eventually cause the blade tojump into the previous cut. Furthermore, if the reciprocating cuttingblade attempts to move counterclockwise about pattern piece B from point60 toward point 62 after pattern piece A has been cut, the materialwithin pattern piece B has a tendency to allow itself to be pushedtoward the interior of pattern piece B by the blade as the cut isinitiated. 4

Cutting pattern piece B in the clockwise rather than a counterclockwisedirection does not alleviate the difficulty of cutting the contours inthe vicinity of point 60 because the symmetric slivers at each side ofpoint 60 present the same difficultics.

The preferred manner of cutting pattern piece B is to advance thecutting blade counterclockwise about the pattern from point 58 to point60 and clockwise about the pattern piece from point 62 to point 60.Cutting the pattern in this manner eliminates the more difficult problemof initiating a cut at the apex of the sliver and allows resort toanother solution for cutting toward point 60.

The problem of cutting toward a point of close approach, such as thepoint 60, can be minimized by two steps. First, the feedrate of thecutting blade 20 illustrated at point 64 along the contour may bereduced as it passes point 64 during movement toward point 60. Reducingthe feedrate of a reciprocating blade driven at a substantially constantreciprocation rate allows a greater number of cutting strokes per unitlength of contour and thereby reduces the tendency of the blade to jumpinto the previous cut along the adjacent contour of pattern piece A.Second, the orientation of the cutting blade about the O-axisperpendicular to the sheet material is changed slightly by adding aO-bias or yaw compensation which rotates the cutting blade slightly andurges the cutting edge of the blade inwardly of the curved contour ofpiece B and away from the adjacent and'previou sly cut contour ofpattern piece A. The combined steps of feedrate reduction or slowdownand yaw compensation allow the blade to move substantially along thecontour of piece B until it reaches point 60. Similar steps are taken asthe blade approaches point 60 from point 62. Slowdown is initiated atpoint 66 together with the slight rotation of the blade out of itstangent relationship as shown to turn the cutting blade inwardly of thecurved contour of piece B and away from the adjacent contour of piece A.The amount of yaw compensation shown in FIG. 3 is greatly exaggeratedmerely to illustrate the concept. In reality, such compensation or thedeparture of the cutting blade from a precisely tangent relationship tothe contour may fall within the range of l-IO. Furthermore,

the amount of compensation may be fixed or increased in either astepwise or continuous manner as the knife approaches point 60. Thecompensation does not have to be initiated simultaneously with nor evenbe accompanied by the feedrate slowdown. The preferred compensation andmanner of introducing the compensation depends upon factors such as thematerial cutting characteristics, the desired accuracy of cut, cuttingblade dimensions, the position of the O-axis relative to the cuttingedge of the blade and others.

It will be noted that the cutting blades 20 illustrated at point 64 and66 are rotated about the 6-axes at points 64 and 66 respectively whichaxes are approximately midway between the leading and trailing edges ofthe blades. Positioning the axis in this manner minimizes thedisplacement of the sheet material due to blade rotation and minimizesthe twisting moment carried through the blade about the O-axis. Theminimization of the material displacement and twisting moment of areciprocating blade is highly desirable. There is less tendency for theblade to break due to the small twisting moment. A twisting of the bladealong the O-axis results in the blade orientation in the upper plies ofthe layup being slightly different from the orientation in the lowerplies. With different orientations, the upper and lower portions of theblade will not track the same cutting path which results in differentcutting paths being followed in the upper and lower plies of the layupand bending or possible breakage of the blade. Also, by rotating areciprocating cutting blade about an axis midway between the leading andtrailing edges, there is less tendency to produce nonintersecting cutsfrom consecutive strokes along a curved cutting path.

Another difficult cutting situation is illustrated in FIG. 4 where partsA and C are shown in closely nested and contacting relationship. Thedifficulty arises because of the intersection of the contours at point70 and the closeness of the pieces at point 72. If pattern piece A hasbeen cut before pattern piece C, and if pattern piece C is cut entirelyin one direction, that is either clockwise or counterclockwise about thepattern piece, the cutting blade will be required to plunge through thelayup and cut away from a point between or the apex of two intersectingcuts. Depending upon the acuteness of the angle between the cuts andtheir proximity, many materials do not permit a cut to be initiated atsuch points. Furthermore, due to the relatively thin sliver 74 ofmaterial between pieces A and C, cutting the contour of pattern piece Cbetween points 70 and 72 may be difficult. The preferred method forcutting the contours shown in FIG. 4 is to 'omit cutting the adjacentcontour of pattern piece A until after the contours of pattern piece Chave been cut. Once pattern piece C has been cut, it is frequentlypossible to cut the adjacent contour of pattern piece A withoutdifficulty.

Sometimes known difficulties cannot be eliminated by the above describedtechniques in which case the order of cutting the contour segments isthen made to depend upon the importance of the contours being cut. Forexample, shoulder cuts for the front panel of suits or shirts are moreimportant than cuts for the bottom hem of trousers or shirts. A hem cutis hidden far below the external edge ofa trouser leg whereas theshoulder cut must be fairly accurate in order to minimize the amount ofmaterial at the shoulder seam. If, for example, the contour of piece Ain FIG. 4 represents a shoulder cut while the adjacent contour of pieceC between points 70 and 72 is a hem cut, it may be essential, contraryto the preferred technique mentioned above, that the contour of part Abe cut first. The segment of piece C adjacent to the sliver 74 is thencut from the midpoint to point 70 and from the midpoint to 72. Slowdownor yaw compensation or both may be required as the blade approachespoints 70 and 72 because of the close proximity of the adjacent,previousy cut contour of pattern piece A. Lastly, the lateral sides ofpattern piece C are cut from point 76 to point 70 and point 77 to 72.The direction, order and manner of cutting in accordance with thegeometric relationship of the contours, the accuracy of the cuts andother factors are all part of cutting protocol.

Another special cutting situation requiring cutting protocol isillustrated in FIG. 5 where pattern pieces D and E are contiguousbetween points 78 and 79. Obviously if pattern piece D is cut beforepattern piece E, the segment between points 78 and 79 need not betraversed again by a cutting blade during the cutting of piece E. Inaddition to save time during the cutting operation and to avoid frayingof the fabric material along the previously cut segment, the segment isomitted entirely from the cutting program for pattern piece E.

Alternatively, it may be desirable to cut the combined profile ofpattern pieces D and E in its entirety and then cut the common contoursof the pattern pieces with a single pass between points 78 and 79.

In each of the cutting situations described above with respect to FIGS.3-5, the order of cuts and the direction of cut along a given contoursegment require that the cutting blade be moved selectively about apattern piece and in two directions, that is clockwise andcounterclockwise. If a cutting tool were caused to cut around a givenpattern piece continuously and in the same direction as the piece wasoriginally digitized on plaque 40, the difficulties mentioned abovecould be avoided only by allowing greater spacing between ajdacentpattern pieces along with the attendant increase in waste material.Cutting around a pattern piece in a single direction would come about inthe two-stage digitizing process simply because it is inherent inprogramming that a pattern piece, without additional information, be cutin the same direction that it is digitized. It is, therefore, necessaryto develop data processing techniques which permit a single patternpiece to be cut in different cutting directions about the pattern pieceand to select portions of the cutting contour to be omitted altogetherfrom the program on the tape 26 or to be placed at different positionsin the program.

The process by which the cutting program is generated with cuttingprotocol is described below in conjunction with the apparatus shown inFIGS. 2 and 6. It will be assumed that a marker layout display has beenmade either manually or by the generator 44 as described above. Theperson operating the digitizer 48 examines the marker layout todetermine those cutting situations which would pose a problem requiringspecial techniques. The person then identifies in the digitized data ofa given pattern piece in the memory 43 those segments which requirecutting in a direction opposite that in which the segments weredigitized or those segments which are omitted or those segments to becut at a later time. The identification can be made by scanning thememory for the identified pattern piece at the previously establishedaddress or addresses and then locating the end points of the contoursegment to be cut in a special manner by placing the reticle of thedigitizer on the end points of the segments as displayed on the markerlayout. Blade down and blade up commands are given with theidentification of the first and last data points respectively of eachsegment. Alternatively, the end points may be designated as from pointsand to points, referring to the directions in which the blade is to moverelative to the points. The data processor 50 is then commanded torearrange the point data defining the identified segments before furtheroperating upon the point data to produce a program tape.

It should be noted that in systems where the marker layout has beengenerated semi-automatically or automatically, the marker layout can beunambiguously defined by data transmitted directly to the pattern memory43 from the generator 44. However, certain ambiguities may exist in thestored information defining the marker layout when the digitizer 48 isused because of the limited accuracy of the two digitizing steps, thefirst with digitizer 42 and the second with digitizer 48. An additionalambiguity can be introduced when the person operating the digitizer 48attempts to locate on the marker layout the end points of the speciallycut segments, again because of the limited accuracy of the digitizingstep which may result in'noncoincidence of the digitized and previouslystored data points. It is preferable to pre-process the digitized andrecorded data by existing resolving techniques to remove suchambiguitie's before the programming routine is entered in the dataprocessor 50.

FIG.'6 illustrates generally the functions performed by the dataprocessor in rearranging the data while a program is generated. Itshould be understood that the complete operation of the data processorincludes introducing other conventional instructions such as knifelifting and plunging commands, feedrate commands and commands relatingto notching and drilling functions. Data processors performingconventional programming of tapes are old in the art and hence thecomplete programming operation performed by the data processor is notshown or described with respect to FIG. 6. Only that portion relating tothe cutting protocol techniques is presented.

Assuming that the information defining the contour of each pattern pieceand the location of each pattern piece inthe marker layout has beenstored in the pattern memory 43, the processor 50 as indicated in theflow chart of FIG. 6 at 80 and 81 locates in the memory the patternpieces and the identified contour segments in accordance with thespecial cutting instructions received from purposes person operating thedigitizer 48. Assuming also for the purpose of discussion that eachpattern piece has been digitized in a clockwise direction, the dataprocessor 50 then readsfrom the memory as shown at 82 the data points ofsegments between the identified segment in the clockwise direction, thatis, the order in which the data points are stored in the memory. Suchdata points are associated with the segments to be cut in the samedirection in which they were digitized. As shown at 83, the processorthen reads the data points along the identified segments in thecounterclockwise direction, that is, the opposite direction in which thepoints are entered in the pattern memory. The newly arranged data pointsare then stored temporarily.

The next operation performed by the processor at 84 is to delete datapoints associated with selected segments which are not to be cut intheir normal turn or which are not to be cut at all simply because theyoverlap or share a common contour with an adjacent pattern piece. Thenthe data points of other selected segments not previously cut are addedto the program at 85. The order in which the two reading, the deletingand the adding steps are performed may be varied depending upon thecutting routine desired.

Once the data points have been rearranged in accordance with thedirection and order in which the contour segments are to be cut, thedata is then processed at 86 by standard servo and curve algorithmsutilized in the past to process point data and produce a cutting programwith basic commands that are understood by the controller 28 and machine12. The program is then stored permanently at 87 on a program tape 26 bythe recorder 52 in FIG. 2.

During the processing of the rearranged data, feedrate slowdown at 88and yaw compensation at 89 may be added by appropriate programmingsubroutines within the data processor 50.

FIG. 7 is a flow diagram representing the information paths in thefeedrate subroutine. The subroutine is entered each time a new datapoint is examined. At the data points, such as points 64 and 66 in FIG.3, an accompanying slowdown command will have been ordered by the personidentifying the segments cut in a special manner.

Following entry into the feedrate subroutine at 90 as shown in FIG. 7,the first matter considered at 91 is whether the cutting blade is up ordown. If the blade is up, the rate of advancement of the tablecarriagesis not governed by the cutting difficulties, but is insteadcontrolled by the length of the movement of the next cutting point. Asindicated at point 92 if the movement is greater than a given amount,for example 1.0 inch, the subroutine at 94 outputs a maximum feedrate inthe program and then returns at 96 to process the next data point. Ifthe movement is not greater than a given amount, then the feedrate iscalculated to be a portion of the maximum rate having the same ratiowith the maximum rate as the commanded displacement does with the unitof movement which is the basis for the decision at 92. The feedratesubroutine then returns at 100 to the next data point.

If the decision at 91 is negative because the cutting blade is down andtherefore engaged with the sheet material being cut, the next decisionmade at 102 is whether the slowdown has been ordered at the data pointunder consideration. If the answer is affirmative, a reduced feedrate istaken from a parameter card inserted in the processor 50 and is recordedin the program as indicated at 104. The subroutine is departed at 106 toprocess the next data point. If slowdown has not been ordered at 102,then the standard feedrate is calculated by applying the maximum rate tothe servo and curve algorithms as in the prior art. In such a case thedata processor returns at 106 to processing the next data point and theprogram will cause the cutting blade to track a contoured segmentwithout modifying the feedrate.

It will be understood that the feedrate subroutine is entered during theprocessing of each data point. However, the decision made at 102 onceset remains fixed until the data point at the end ofa curve requiringslowdown is reached together with an accompanying reset command. Theindividual operating the digitizer will have previously recorded theresetting command with that particular data point. Normal feedratecommands are generated thereafter.

FIG. 8 discloses the subroutine within the data processor which controlsthe O-angle of the cutting blade at each data point. This subroutineduring conventional processing of the point data calculates theincremental rotation required to maintain the cutting blade tangent to acurved cutting path at each point. The subroutine is modified asillustrated to permit the introduction of yaw compensation to turn theblade to one side or the other of the cutting path and away from anadjacent and previously cut contour segment.

The subroutine is entered at 110 and the first function performed at 112is calculating the angle of the cutting path to the next data point onthe cutting path. The next step at 114 is calculating the incrementalrotation of the blade about the -axis to maintain the blade in itsgenerally tangent relationship to the cutting path. The incrementalrotation including the direction of rotation, that is for example,positive for incremental rotations in the counterclockwise direction andnegative for incremental rotations in the clockwise direction, areapplied to the yaw branch 116. The yaw branch is set by the individualintroducing the yaw commands from the digitizer 48 in FIG. '2 atselected points along the cutting contours, such as points 64 and 66 inFIG. 3. The yaw branch, once set by the individual remains set until theyaw command is either removed or changed.

Assuming that a yaw left command illustrated at point 64 in FIG. 3 hasbeen imposed on the yaw branch 116, the left branch in FIG. 8 isfollowed to 118. It is then necessary to determine what the direction ofthe rotation calculated at 114 was. If the rotation is negative so thatthe blade is rotated clockwise or to the right of the cutting path and ayaw left compensation has been ordered, it is necessary to subtract thecompensation angle from the calculated rotation as indicated at 120. Thedata processing is then returned at 124 to the calculations for the nextdata point. If the direction of rotation is positive orcounterclockwise, it is necessary to add the yaw left command to thecalculated rotation as indicated at 122. i

If yaw right illustrated in FIG. 3 at point 66 has been ordered at thebranch 116, the right branch is followed to 126. If the rotation isnegative or clockwise, yaw compensation is added to the calculatedrotation at 128 and the subroutine returns to the next data point at130. If the rotation is positive or counterclockwise, the yawcompensation must be subtracted from the calculated rotation asindicated at 132.

If no yaw command has been ordered at the branch 116 or after the yawcommand has been removed, the calculated increment of rotation isrecorded in the program and the subroutine returns at 134.

It will thus be seen that the cutting program generated by the dataprocessor described above does not follow the contour segments in thesame order in which.

the segments were digitized. Selected cutting sequences and directionsof cut are established to carry out the cutting operation with the leastdifficulty and the greatest accuracy. In contrast to the programsemployed in the past, it is possible to cut closely spaced andcontiguous pattern pieces more successfully.

While the present invention has been described in several differentembodiments, it should be understood that further modifications andsubstitutions can be had without departing from the spirit of theinvention. For example, the specific cutting situations illustrated inFIGS. 3, 4 and 5 are merely exemplary of the difficulties encounteredwhen pattern pieces are closely nested in a marker layout. The geometricfigures represented may, of course,-be varied but the same generalproblems associated with points of closest approach may still beencountered. It should also be understood that the severity of problemsassociated with points of closest approach or contiguous contours willvary in accordance with other factors such as the type of material beingcut and its cutting characteristics, the type of cutting tool beingutilized and the cutting characteristics of the tool including itssharpness, rate of reciprocation or other movement relative to the sheetmaterial and dimensions. The described cutting techniques may be usedsingly or in combination. For example, it is possible to utilizeslowdown without yawing or to change the direction of cut about thepattern piece segments without slowdown and yawing. Accordingly, thepresent invention has been described in several preferred forms merelyby way of illustration rather than limitation.

We claim:

1. A system for cutting a plurality of pattern pieces from sheetmaterial in accordance with a marker layout including each of the piecesin spaced relationship comprising: first means for reducing the contoursof the pattern pieces in the marker layout to point data form; secondmeans for identifying by point data the segments of the pattern contoursto be cut and the cutting direction about the pattern pieces for eachsegment; data processing means receiving the point data and identifiedsegments with their cutting directions for generating cutting commandsin accordance with the point data and directional information; andcutting means for cutting the pattern pieces from sheet material inresponse to the commands.

2. A system for cutting a plurality of pattern pieces as defined inclaim 1 further including memory means for holding the cutting commandsin storage after being generated.

3. A system for cutting a plurality of pattern pieces as defined inclaim 1 wherein the first and second means comprise a coordinatedigitizer.

4. A system for cutting pattern pieces from sheet material comprising:first digitizing means for converting the contours of each pattern pieceinto sequences of point data corresponding to the order of the pointsalong the contours; second digitizing means for locating the patternpieces in a marker layout and identifying the data points associatedwith selected segments of the pattern piece contours to be cut in adirection opposite the given direction; data handling means connected tothe first and second digitizing means for arranging in reverse order thesequential point data defining the selected segments of the patternpiece contours to produce reverse sequences and for referencing thesequences of the point data including the reverse sequences to themarker layout; means for producing cutting commands for moving a cuttingtool along a cutting path through points on the contours represented bythe point data and in the directions on the marker layout correspondingrespectively to the sequences of point data referenced to the markerlayout by the data handling means; and cutting means for cutting thepattern pieces from the sheet material in accordance with the cuttingcommands.

5. A method of processing cutting information for a cutting machinewhich advances a cutting tool along a programmed cutting path followingthe contours of pattern pieces to be cut from a sheet materialcomprising: individually digitizing the complete contour of each patternpiece in a singular direction about any given piece to produce pointdata defining the contours; generating a marker layout defining thepositional relationship of the pattern pieces with respect to oneanother in the sheet material from which the pieces are to be cut;producing additional point data defining the placement of the patternpieces in the layout; identifying in the point data selected segments ofthe pattern piece contours to be cut in a direction opposite to thesingular direction in which the given pieces were individuallydigitized; and processing the digitized data to produce a cuttingprogram for advancing the cutting tool along the selected segments ofthe pattern piece contours in the direction opposite that of thedigitizing and along other contour segments in the direction of thedigitizing.

6. Amethodof processing cutting information as defined in claimSincluding the additional step of omitting from a portion of the programassociated with a given pattern piece having a contour segment closelyspaced to another pattern piece point data associated with the closelyspaced segment.

7. A method of processing cutting information as defined in claim 5further including the step of adding to a cutting program maintaining acutting blade advanced along the cutting path substantially tangent tothe contour at each point a bias turning the blade slightly off thetangent and away from an adjacent contour segment.

8. A method of processing cutting information as defined in claim 5further including the step of adding to a cutting program a reducedfeedrate along the cutting path segments where the tool tangentiallyapproaches previously cut segments. 7

9. A method of processing cutting information as defined in claim 5wherein: the step of individually digitizing includes digitizingreference points for each pattern piece in the digitized data; and thestep of producing additional point data comprises digitizing thelocation of the reference points of the pattern pieces in the markerlayout.

10. A method of processing cutting information as defined in claim 5including the additional step of omit ting from the program associatedwith a given pattern piece having a contour segment common with acontiguous pattern piece programmed cutting of the common segment.

1. A system for cutting a plurality of pattern pieces from sheetmaterial in accordance with a marker layout including each of the piecesin spaced relationship comprising: first means for reducing the contoursof the pattern pieces in the marker layout to point data form; secondmeans for identifying by point data the segments of the pattern contoursto be cut and the cutting direction about the pattern pieces for eachsegment; data processing means receiving the point data and identifiedsegments with their cutting directions for generating cutting commandsin accordance with the point data and directional information; andcutting means for cutting the pattern pieces from sheet material inresponse to the commands.
 2. A system for cutting a plurality of patternpieces as defined in claim 1 further including memory means for holdingthe cutting commands in storage after being generated.
 3. A system forcutting a plurality of pattern pieces as defined in claim 1 wherein thefirst and second means comprise a coordinate digitizer.
 4. A system forcutting pattern pieces from sheet material comprising: first digitizingmeans for converting the contours of each pattern piece into sequencesof point data corresponding to the order of the points along thecontours; second digitizing means for locating the pattern pieces in amarker layout and identifying the data points associated with selectedsegments of the pattern piece contours to be cut in a direction oppositethe given direction; data handling means connected to the first andsecond digitizing means for arranging in reverse order the sequentialpoint data defining the selected segments of the pattern piece contoursto produce reverse sequences and for referencing the sequences of thepoint data including the reverse sequences to the marker layout; meansfor producing cutting commands for moving a cutting tool along a cuttingpath through points on the contours represented by the point data and inthe directions on the marker layout corresponding respectively to thesequences of point data referenced to the marker layout by the datahandling means; and cutting means for cutting the pattern pieces fromthe sheet material in accordance with the cutting commands.
 5. A methodof processing cutting information for a cutting machine which advances acutting tool along a programmed cutting path following the contours ofpattern pieces to be cut from a sheet material comprising: individuallydigitizing the complete contour of each pattern piece in a singulardirection about any given piece to produce point data defining thecontours; generating a marker layout defining the positionalrelationship of the pattern pieces with respect to one another in thesheet material from which the pieces are to be cut; producing additionalpoint data defining the placement of the pattern pieces in the layout;identifying in the point data selected segments of the pattern piececontours to be cut in a direction opposite to the singular direction inwhich the given pieces were individually digitized; and processing thedigitized data to produce a cutting program for advancing the cuttingtool along the selected Segments of the pattern piece contours in thedirection opposite that of the digitizing and along other contoursegments in the direction of the digitizing.
 6. A method of processingcutting information as defined in claim 5 including the additional stepof omitting from a portion of the program associated with a givenpattern piece having a contour segment closely spaced to another patternpiece point data associated with the closely spaced segment.
 7. A methodof processing cutting information as defined in claim 5 furtherincluding the step of adding to a cutting program maintaining a cuttingblade advanced along the cutting path substantially tangent to thecontour at each point a bias turning the blade slightly off the tangentand away from an adjacent contour segment.
 8. A method of processingcutting information as defined in claim 5 further including the step ofadding to a cutting program a reduced feedrate along the cutting pathsegments where the tool tangentially approaches previously cut segments.9. A method of processing cutting information as defined in claim 5wherein: the step of individually digitizing includes digitizingreference points for each pattern piece in the digitized data; and thestep of producing additional point data comprises digitizing thelocation of the reference points of the pattern pieces in the markerlayout.
 10. A method of processing cutting information as defined inclaim 5 including the additional step of omitting from the programassociated with a given pattern piece having a contour segment commonwith a contiguous pattern piece programmed cutting of the commonsegment.